Abstract: Cocaine use among criminal offenders constitutes a major public health problem and is tied to negative consequences for offenders, their families, and their communities. One of the direst of these consequences is repeated incarceration; thus, interventions that reduce criminal recidivism are needed. Forensic populations are often viewed with considerable therapeutic pessimism. However, offenders exhibit heterogeneity in personality traits, and the assessment of individual differences among offenders may provide valuable information that guides the use of psychotherapeutic interventions. Among offenders, psychopathy has emerged as an important personality construct for the understanding of violence and criminal recidivism. Moreover, core traits of psychopathy such as lack of empathy, deceitfulness, and lack of remorse may have negative implications for the efficacy of psychosocial interventions. A foundational premise of the present work is that understanding the moderating role of psychopathic traits on substance use treatment outcomes among offenders is essential to determining what works, and for whom. The current proposal is a Phase II randomized clinical trial that aims to examine the impact of psychopathic traits on the efficacy of a brief cocaine use intervention for offenders in a jail diversion program. Hypotheses that will be examined include: 1) that a Motivational Interviewing (MI) - based treatment will reduce cocaine use and related consequences relative to a Standard Care only condition, 2) that the reduction in cocaine use in the intervention group will mediate a reduction in later criminal recidivism relative to the Standard Care condition, and 3) that core psychopathic traits will moderate the efficacy of the intervention such that individuals with lower levels of these traits will derive greater benefits with regard to decreased cocaine use, decreased drug use consequences, and decreased criminal recidivism at a one-year follow-up. This work has the potential to provide important data regarding which individuals can benefit from a brief intervention for cocaine use. Such data will inform the effective and efficient allocation of treatment resources for cocaine using offenders.